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I, Screechy 



Makej Projects 



I, Screechy 

Written By: Mahesh Venkitachalam 



TOOLS: 




PARTS: 


Dremel tool with cuttignq, qrindinq, or 
routina bits (1) 




555 Timer IC (RadioShack #276-1723) 
ill 


Solderina/desolderinq tools (1) 




4040 -12 bit counter IC (1) 




• 


On/off switch (1) 




• 


LDR Liqht Sensor (1) 




• 


5mm Blue LED Radio Shack Part #210- 
2850 (2) 




• 


LED. Redd) 




• 


Beeper/Buzzer (1) 




• 


BC 549- transistor (1) 




• 


Resistor. 10kQ. 1/8WM) 




• 


Resistors. 1kQ (2) 




• 


2.2 uF capacitor (1) 




• 


9V battery M) 



SUMMARY 

This project is an attempt at designing a simple toy based on the principle of a light sensitive 
oscillator. It produces sound and light that vary in frequency with the intensity of light falling 
on it. 



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I, Screechy 



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I, Screechy 



Step 1 — 1, Screechy 




• Download schematic and PCB files in EAGLE format from here . 

• The circuit works using a combination of an oscillator and a frequency divider. You can 
read an explanation here . 

Step 2 




• You can use a general-purpose PCB for this project. But it's much cleaner to use a custom 
PCB. 

• You can easily make a PCB at home using the toner transfer technique described in this 
link . 

• Using the above link as guide, print out the PCB design on photo paper on a laser printer, 
iron it on to the copper laminate, and once the toner sticks, etch it out with ferric chloride. 
You can then drill holes in the PCB using a 0.8 mm bit on a Dremel tool. 



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I, Screechy 



Step 3 











- 




• 










I*' 


H 








t 


1 




- 









• A pencil drawing on the non-copper side of the PCB will help you place the components 
easily. There are 2 connections that need to routed over the board manually using wires. 
Connect a wire between the two points labeled "A", and another wire between the two 
points labeled "B". 

• Solder the components on to the PCB. 



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• Use a dremel or any other tool of choice to cut holes for the LEDs, LDR, and switch. 

• Solder wires to LEDs, LDR and switch, and fix them on to the enclosure before soldering 
the other end of the wires to the PCB. I did it in the opposite order first and had to cut the 
wires to fix it! 

• Drill some holes in the cap to let the sound out. 

• Insert the PCB and 9V battery into the bottle. Place a small sheet of plastic in between to 
protect the PCB's solder joints from shorting on the battery. 

• Enjoy your screechy robot! 



Read more details about the project here: 
http://electronut.in/projects/i-screechy... 



st generated on 2013-01-21 10:45:48 AM. 



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